1. Field of the Invention
The present invention generally relates to projecting a two-dimensional image of high quality especially in color.
2. Description of the Related Art
It is generally known to project a two-dimensional image on a projection surface based on a pair of scan mirrors which oscillate in mutually orthogonal directions to scan a laser beam over a raster pattern comprised of a plurality of scan lines. The image is created in the raster pattern by energizing or pulsing a laser on and off at selected times, thereby illuminating selected pixels with a beam spot and not illuminating other pixels in each scan line. The number of distinct beam spots or pixels that can fit in each scan line is known as the resolution.
One of the scan mirrors, sometimes referred to herein as an X-mirror, sweeps the laser beam at a relatively faster speed generally along a scan direction extending along the horizontal, and the other of the scan mirrors, sometimes referred to herein as a Y-mirror, sweeps the scan line at a relatively slower speed generally perpendicular to the scan direction extending along the vertical. The X-mirror is oscillated, typically at resonance, at a scan frequency and at a speed that varies along each scan line. Thus, the X-mirror has a maximum speed at the center of each scan line and a minimum speed at the ends of each scan line.
The variable speed of the X-mirror causes the pixels to have variable time durations in order to obtain pixels of the same size on the projection surface. The variable speed of the X-mirror also causes the pixels to have a variable brightness, that is, the projected image appears brighter at those pixels where the X-mirror has a slower speed. These variable time durations and the variable brightness must be taken into account in order to project the image with uniformly sized pixels and uniform brightness.